The present invention relates to an improvement in controlling the quantity of fluid delivered to a header and discharged in turn by the header to an object to be treated by the fluid. While the invention is considered to have a wide range of applications, for the purpose of explanation, it will be discussed as applied to the cooling of hot strip while being rolled or immediately after rolling in a rolling mill.
In the operation of a continuous hot strip rolling mill, and particularly the finishing train thereof, two important considerations are involved as far as the control of the temperature of the strip by removal of heat is concerned. The temperature of a given strip as it immediately leaves the last stand of the finishing train, for metallurgical reasons, must be maintained at a predetermined temperature. Similarly the temperature of a given strip as it reaches the downcoiler, again for metallurgical reasons, must be maintained at a predetermined temperature; howbeit, at a different temperature than the strip finishing temperature. These two fundamental requisites in the past have required that as to the finishing stand temperature, the speed of the finishing train be regulated to assure that the proper temperature was obtained, and as to the downcoiler temperature, the strip, after leaving the last stand of the finishing train was subjected to a controlled application of cooling water above and below the strip.
In more recent hot strip mills, as the demand for greater tonnage, the requirement to roll more difficult products, and need for superior quality were imposed, the strip cooling systems expanded substantially in size and capacity and control sophistication. This has resulted in providing cooling systems which were extremely complicated, expensive and unreliable. For example, in the desire for automation and quick and fine control of the strip temperature, the attendant temperature of the strip produced in the runout cooling system is controlled by a digital feedback computer system in conjunction with literally hundreds of electronic and hydraulic components.
In the past, in a very limited way, fixed hydraulic head overflow pipes have been employed to control the quantity of fluid delivered to the headers of hot strip rolling mill runout cooling systems, but such an approach has never been attempted as an analog control of the volume of the coolant fluid by employing multiple fixed overflow pipes designed to cover the entire temperature requirements of the hot strip mill; nor have they been employed in this context, as interstand cooling units.